ALBERT

Description: In 2004 NASA began investigation of a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would require estimates of the HST attitude and rates in order to achieve a capture by the proposed Hubble robotic vehicle (HRV). HRV was to be equipped with vision-based sensors, capable of estimating the relative attitude between HST and HRV. The inertial HST attitude is derived from the measured relative attitude and the HRV computed inertial attitude. However, the relative rate between HST and HRV cannot be measured directly. Therefore, the HST rate with respect to inertial space is not known. Two approaches are developed to estimate the HST rates. Both methods utilize the measured relative attitude and the HRV inertial attitude and rates. First, a nonlinear estimator is developed. The nonlinear approach estimates the HST rate through an estimation of the inertial angular momentum. The development includes an analysis of the estimator stability given errors in the measured attitude. Second, a linearized approach is developed. The linearized approach is a pseudo-linear Kalman filter. Simulation test results for both methods are given, including scenarios with erroneous measured attitudes. Even though the development began as an application for the HST robotic servicing mission, the methods presented are applicable to any rendezvous/capture mission involving a non-cooperative target spacecraft.

Description: There is no doubt that the awareness of the often long history and its principal players of a scientific specialty is disappearing among present-day researchers. The reason is the inexorable rise of specialization, in which scientists are expected to keep pace with publications in their own field, not to mention the inevitable round of writing grant proposals and teaching and other mundane responsibilities. The authors of this small book had the intention of rectifying this for solar and stellar physics, disciplines which are still broad enough to embrace fields as diverse as nuclear fusion, magnetohydrodynamics, and the dynamic theory of gas spheres. They take the reader on a journey from ancient Greek and middle Eastern astronomy to the late 1990s, one which has an emphasis very much on a theoretical point of view. For the authors, it is the ideas that are central, not the observations.

Description: I compare the burst detection sensitivity of CGRO's BATSE, Swift's BAT, the GLAST Burst Monitor (GBM) and EXIST as a function of a burst s spectrum and duration. A detector's overall burst sensitivity depends on its energy sensitivity and set of accumulations times (Delta)t; these two factors shape the detected burst population. For example, relative to BATSE, the BAT s softer energy band decreases the detection rate of short, hard bursts, while the BAT s longer accumulation times increase the detection rate of long, soft bursts. Consequently, Swift is detecting long, low fluence bursts (2-3 x fainter than BATSE).

Description: Experimental results and interpretation of the temperature measurements data retrieved during the balloon campaigns (in 2002 and in 2003) for testing HASI (Huygens Atmospheric Structure Instrument), launched from the Italian Space Agency Base in Trapani (Sicily), are presented. Both ascending and descending phases are analysed; data reveal interesting features near the tropopause (present in the region between 11km-14km), where temperature cooling can be related to layers with strong winds (2002 flight); in the troposphere a multistratified structure of the temperature field is observed and discussed (particularly in the 2003 flight) Finally, stability and turbulence of the atmosphere are analysed; the buoyancy N2 parameters for both the flights show lowers value respect to standard tropospheric values corresponding to a lower stability of the atmosphere; still there is a higher stability above the tropopause. The energy spectrum of temperature data is consistent with the Kolmogorov theory: the characteristic k(sup -5/3) behaviour is reproduced.

Description: As part of the collaboration with Italian Space Agency on HASI instrument for Huygens mission, University of Padova has been conducting since 2001 scientific activity on Stratospheric Balloon Launches from the Trapani base in Sicily. The most recent boomerang flight in July 2003 has successfully flown a mock up of the Huygens probe hosting spares of flight scientific units and extra housekeeping and scientific sensors on a parachuted descent from 33 kilometre altitude. This work presents the studies conducted on attitude reconstruction of the probe, as well as the utilisation of iterative extended Kalman filtering in investigating vanes induced spin rate and in providing a baseline for the performance evaluation of Huygens accelerometers operations. Finally some possible contributions on the reconstruction of the lower part of Titan descent for Huygens probe are suggested based on the confrontation of sensor data for 2003 flight.

Description: Missions with planned launch dates several years from today pose significant design challenges in properly accounting for technology advances that may occur in the time leading up to actual spacecraft design, build, test and launch. Conceptual mission and spacecraft designs that rely solely on off the shelf technology will result in conservative estimates that may not be attractive or truly representative of the mission as it actually will be designed and built. This past summer, as part of one of NASA s Vision Mission Studies, a group of students at the Laboratory for Spacecraft and Mission Design (LSMD) have developed and analyzed different Neptune mission baselines, and determined the benefits of various assumed technology improvements. The baseline mission uses either a chemical propulsion system or a solar-electric system. Insertion into orbit around Neptune is achieved by means of aerocapture. Neptune s large moon Triton is used as a tour engine. With these technologies a comprehensive Cassini-class investigation of the Neptune system is possible. Technologies under investigation include the aerocapture heat shield and thermal protection system, both chemical and solar electric propulsion systems, spacecraft power, and energy storage systems.

Description: Entry probes provide useful insights into the structures of planetary atmospheres, but give only one-dimensional pictures of complex four-dimensional systems that vary on all temporal and spatial scales. This makes the interpretation of the results quite challenging, especially as regards atmospheric dynamics. Here is a planetary meteorologist's vision of what the next generation of atmospheric entry probe missions should be: Dedicated sounding instruments get most of the required data from orbit. Relatively simple and inexpensive entry probes are released from the orbiter, with low entry velocities, to establish ground truth, to clarify the vertical structure, and for adaptive observations to enhance the dataset in preparation for sensitive operations. The data are assimilated onboard in real time. The products, being immediately available, are of immense benefit for scientific and operational purposes (aerobraking, aerocapture, accurate payload delivery via glider, ballooning missions, weather forecasts, etc.).

Description: A viewgraph presentation is shown to raise awareness of aerocapture technology through in-space propulsion. The topics include: 1) Purpose; 2) In-Space Propulsion Program; 3) Aerocapture Overview; 4) Aerocapture Technology Alternatives; 5) Aerocapture Technology Project Process; 6) Results from 2002 Aerocapture TAG; 7) Bounding Case Requirements; 8) ST9 Flight Demonstration Opportunity; 9) Aerocapture NRA Content: Cycles 1 and 2; 10) Ames Research Center TPS Development; 11) Applied Research Associates TPS Development; 12) LaRC Structures Development; 13) Lockheed Martin Astronautics Aeroshell Development; 14) ELORET/ARC Sensor Development; 15) Ball Aerospace Trailing Ballute Development; 16) Cycle 2 NRA Selections - Aerocapture; and 17) Summary.

Description: Mars Pathfinder's Accelerometer instrument measured an unexpected and large temperature inversion between 10 and 20 kilometer altitude. Other instruments have failed to detect similar temperature inversions. I test whether this inversion is real or not by examining what changes have to be made to the assumptions in the accelerometer data processing to obtain a more "expected" temperature profile. Changes in derived temperature of up to 30K, or 15%, are necessary, which correspond to changes in derived density of up to 25% and changes in derived pressure of up to 10%. If the drag coefficient is changed to satisfy this, then instead of decreasing from 1.6 to 1.4 from 20 kilometers to 10 kilometers, the drag coefficient must increase from 1.6 to 1.8 instead. If winds are invoked, then speeds of 60 meters per second are necessary, four times greater than those predicted. Refinements to the equation of hydrostatic equilibrium modify the temperature profile by an order of magnitude less than the desired amount. Unrealistically large instrument drifts of 0.5-1.0 meters per square second are needed to adjust the temperature profile as desired. However, rotational contributions to the accelerations may have the necessary magnitude and direction to make this correction. Determining whether this hypothesis is true will require further study of the rigid body equations of motion, with detailed knowledge of the positions of all six accelerometers. The paradox concerning this inversion is not yet resolved. It is important to resolve it because the paradox has some startling implications. At one extreme, are temperature profiles derived from accelerometers inherently inaccurate by 20K or more? At the other extreme, are RS temperature profiles inaccurate by this same amount?

Description: We explore the utility of various sensors by recovering parachute-probe dynamics information from a package released from a small-scale, remote-controlled airplane. The airdrops aid in the development of datasets for the exploration of planetary probe trajectory recovery algorithms, supplementing data collected from instrumented, full-scale tests and computer models.